[PATCH] Remove limit on number of GEMDOS HD DTA structures

[Eero Tamminen <oak@xxxxxxxxxxxxxx>]

Allocate more Hatari side DTA cache entries on demand, instead of
using fixed array of 256 entries.

To reduce cache size, check whether Fsfirst() uses an earlier DTA,
and if yes, re-use that one from cache.

If cache grows too large (>32k entries), use it as a ring buffer,
same as earlier.  This can happen with very long Hatari run, as
there's no GEMDOS call for freeing DTAs.

TODO:

Cache growth could be limited further by keeping track to which
process each DTA belongs to (maybe by basepage address?), and when
that process Pterm() is caught, marking those DTAs as unused, and
seting DTAIndex to first free entry.

DTAIndex increment would then either pick next free entry, allocate
more if there are no free ones, or wrap to zero if cache size limit is
reached.
---
 src/gemdos.c | 106 ++++++++++++++++++++++++++++++++++++---------------
 1 file changed, 76 insertions(+), 30 deletions(-)

diff --git a/src/gemdos.c b/src/gemdos.c
index aa851d00..f7fd7806 100644
--- a/src/gemdos.c
+++ b/src/gemdos.c
@@ -101,8 +101,8 @@ typedef struct {
 } DTA;
 
 #define DTA_MAGIC_NUMBER  0x12983476
-#define MAX_DTAS_FILES    256      /* Must be ^2 */
-#define MAX_DTAS_MASK     (MAX_DTAS_FILES-1)
+#define DTA_CACHE_START   0x40     /* initial DTA cache size (grows on demand) */
+#define DTA_CACHE_MAX     0x8000   /* max DTA cache size to (half of what 16-bit DTA index can index) */
 
 #define  BASE_FILEHANDLE     64    /* Our emulation handles - MUST not be valid TOS ones, but MUST be <256 */
 #define  MAX_FILE_HANDLES    32    /* We can allow 32 files open at once */
@@ -135,6 +135,7 @@ typedef struct
 typedef struct
 {
 	bool bUsed;
+	Uint32 addr;                        /* ST-RAM DTA address for matching reused entries */
 	int  nentries;                      /* number of entries in fs directory */
 	int  centry;                        /* current entry # */
 	struct dirent **found;              /* legal files */
@@ -142,8 +143,9 @@ typedef struct
 } INTERNAL_DTA;
 
 static FILE_HANDLE  FileHandles[MAX_FILE_HANDLES];
-static INTERNAL_DTA InternalDTAs[MAX_DTAS_FILES];
-static int DTAIndex;        /* Circular index into above */
+static INTERNAL_DTA *InternalDTAs;
+static int DTACount;        /* Current DTA cache size */
+static Uint16 DTAIndex;     /* Circular index into above */
 static Uint16 CurrentDrive; /* Current drive (0=A,1=B,2=C etc...) */
 static Uint32 act_pd;       /* Used to get a pointer to the current basepage */
 static Uint16 nAttrSFirst;  /* File attribute for SFirst/Snext */
@@ -361,11 +363,19 @@ static void ClearInternalDTA(int idx)
 /*-----------------------------------------------------------------------*/
 /**
  * Clear all DTA cache structures.
+ *
+ * If there are no DTA structures yet, allocate default amount
  */
 static void GemDOS_ClearAllInternalDTAs(void)
 {
 	int i;
-	for(i = 0; i < ARRAY_SIZE(InternalDTAs); i++)
+	if (!InternalDTAs)
+	{
+		DTACount = DTA_CACHE_START;
+		InternalDTAs = calloc(DTACount, sizeof(*InternalDTAs));
+		assert(InternalDTAs);
+	}
+	for(i = 0; i < DTACount; i++)
 	{
 		ClearInternalDTA(i);
 	}
@@ -2775,10 +2785,10 @@ static int GemDOS_Pexec(Uint32 Params)
 static bool GemDOS_SNext(void)
 {
 	struct dirent **temp;
-	int Index;
 	int ret;
 	DTA *pDTA;
 	Uint32 DTA_Gemdos;
+	Uint16 Index;
 
 	LOG_TRACE(TRACE_OS_GEMDOS, "GEMDOS 0x4F Fsnext() at PC 0x%X\n" , CallingPC);
 
@@ -2800,16 +2810,17 @@ static bool GemDOS_SNext(void)
 		return false;
 	}
 
-	/* Find index into our list of structures */
-	Index = do_get_mem_word(pDTA->index) & MAX_DTAS_MASK;
-
 	if (nAttrSFirst == GEMDOS_FILE_ATTRIB_VOLUME_LABEL)
 	{
 		/* Volume label was given already in Sfirst() */
 		Regs[REG_D0] = GEMDOS_ENMFIL;
 		return true;
 	}
-	if (!InternalDTAs[Index].bUsed)
+
+	/* Find index into our list of structures */
+	Index = do_get_mem_word(pDTA->index);
+
+	if (Index >= DTACount || !InternalDTAs[Index].bUsed)
 	{
 		/* Invalid handle, TOS returns ENMFIL
 		 * (if Fsetdta() has been used by any process)
@@ -2861,9 +2872,10 @@ static bool GemDOS_SFirst(Uint32 Params)
 	struct dirent **files;
 	int Drive;
 	DIR *fsdir;
-	int i,j,count;
+	int i, j, count;
 	DTA *pDTA;
 	Uint32 DTA_Gemdos;
+	Uint16 useidx;
 
 	/* Find filename to search for */
 	pszFileName = (char *)STMemory_STAddrToPointer(STMemory_ReadLong(Params));
@@ -2893,19 +2905,36 @@ static bool GemDOS_SFirst(Uint32 Params)
 		return true;
 	}
 
-	/* Atari memory modified directly with do_mem_* + strcpy() -> flush the data cache */
+	/* Atari memory will be modified (below) directly with
+	 * do_mem_* + strcpy() -> flush the data cache
+	 */
 	M68000_Flush_Data_Cache(DTA_Gemdos, sizeof(DTA));
 
 	pDTA = (DTA *)STMemory_STAddrToPointer(DTA_Gemdos);
 
+	/* re-use earlier Hatari DTA? */
+	if (do_get_mem_long(pDTA->magic) == DTA_MAGIC_NUMBER)
+	{
+		useidx = do_get_mem_word(pDTA->index);
+		if (useidx >= DTACount || InternalDTAs[useidx].addr != DTA_Gemdos)
+			useidx = DTAIndex;
+	}
+	else
+	{
+		/* set our magic num on new Hatari DTA */
+		do_put_mem_long(pDTA->magic, DTA_MAGIC_NUMBER);
+		useidx = DTAIndex;
+	}
+
 	/* Populate DTA, set index for our use */
-	do_put_mem_word(pDTA->index, DTAIndex);
-	/* set our dta magic num */
-	do_put_mem_long(pDTA->magic, DTA_MAGIC_NUMBER);
+	do_put_mem_word(pDTA->index, useidx);
 
-	if (InternalDTAs[DTAIndex].bUsed == true)
-		ClearInternalDTA(DTAIndex);
-	InternalDTAs[DTAIndex].bUsed = true;
+	if (InternalDTAs[useidx].bUsed == true)
+	{
+		ClearInternalDTA(useidx);
+	}
+	InternalDTAs[useidx].bUsed = true;
+	InternalDTAs[useidx].addr = DTA_Gemdos;
 
 	/* Were we looking for the volume label? */
 	if (nAttrSFirst == GEMDOS_FILE_ATTRIB_VOLUME_LABEL)
@@ -2920,8 +2949,8 @@ static bool GemDOS_SFirst(Uint32 Params)
 	/* open directory
 	 * TODO: host path may not fit into InternalDTA
 	 */
-	fsfirst_dirname(szActualFileName, InternalDTAs[DTAIndex].path);
-	fsdir = opendir(InternalDTAs[DTAIndex].path);
+	fsfirst_dirname(szActualFileName, InternalDTAs[useidx].path);
+	fsdir = opendir(InternalDTAs[useidx].path);
 
 	if (fsdir == NULL)
 	{
@@ -2931,7 +2960,7 @@ static bool GemDOS_SFirst(Uint32 Params)
 	/* close directory */
 	closedir(fsdir);
 
-	count = scandir(InternalDTAs[DTAIndex].path, &files, 0, alphasort);
+	count = scandir(InternalDTAs[useidx].path, &files, 0, alphasort);
 	/* File (directory actually) not found */
 	if (count < 0)
 	{
@@ -2939,9 +2968,9 @@ static bool GemDOS_SFirst(Uint32 Params)
 		return true;
 	}
 
-	InternalDTAs[DTAIndex].centry = 0;          /* current entry is 0 */
+	InternalDTAs[useidx].centry = 0;          /* current entry is 0 */
 	dirmask = fsfirst_dirmask(szActualFileName);/* directory mask part */
-	InternalDTAs[DTAIndex].found = files;       /* get files */
+	InternalDTAs[useidx].found = files;       /* get files */
 
 	/* count & copy the entries that match our mask and discard the rest */
 	j = 0;
@@ -2950,7 +2979,7 @@ static bool GemDOS_SFirst(Uint32 Params)
 		Str_DecomposedToPrecomposedUtf8(files[i]->d_name, files[i]->d_name);   /* for OSX */
 		if (fsfirst_match(dirmask, files[i]->d_name))
 		{
-			InternalDTAs[DTAIndex].found[j] = files[i];
+			InternalDTAs[useidx].found[j] = files[i];
 			j++;
 		}
 		else
@@ -2959,23 +2988,40 @@ static bool GemDOS_SFirst(Uint32 Params)
 			files[i] = NULL;
 		}
 	}
-	InternalDTAs[DTAIndex].nentries = j; /* set number of legal entries */
+	InternalDTAs[useidx].nentries = j; /* set number of legal entries */
 
 	/* No files of that match, return error code */
 	if (j==0)
 	{
 		free(files);
-		InternalDTAs[DTAIndex].found = NULL;
+		InternalDTAs[useidx].found = NULL;
 		Regs[REG_D0] = GEMDOS_EFILNF;        /* File not found */
 		return true;
 	}
 
 	/* Scan for first file (SNext uses no parameters) */
 	GemDOS_SNext();
-	/* increment DTA index */
-	DTAIndex++;
-	DTAIndex &= MAX_DTAS_MASK;
 
+	/* increment DTA buffer index unless earlier one was reused */
+	if (useidx != DTAIndex)
+		return true;
+
+	if (++DTAIndex >= DTACount)
+	{
+		if (DTACount < DTA_CACHE_MAX)
+		{
+			/* double DTA cache size */
+			InternalDTAs = realloc(InternalDTAs, 2 * DTACount * sizeof(*InternalDTAs));
+			assert(InternalDTAs);
+			memset(InternalDTAs + DTACount, 0, DTACount * sizeof(*InternalDTAs));
+			DTACount *= 2;
+		}
+		else
+		{
+			Log_Printf(LOG_WARN, "Too many (%d) active GEMDOS HD DTA entries, wrapping index\n", DTAIndex);
+			DTAIndex = 0;
+		}
+	}
 	return true;
 }
 
@@ -3694,7 +3740,7 @@ void GemDOS_Info(FILE *fp, Uint32 bShowOpcodes)
 	}
 
 	fputs("\nInternal Fsfirst() DTAs:\n", fp);
-	for(used = i = 0; i < ARRAY_SIZE(InternalDTAs); i++)
+	for(used = i = 0; i < DTACount; i++)
 	{
 		int j, centry, entries;
 
-- 
2.20.1


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